This invention relates to alumina ceramic bodies containing dispersed metal for use as cutting tools, wear parts, and the like. In particular the invention relates to such bodies containing a metal including both nickel and aluminum and an additional phase of silicon carbide.
Ceramic-metal or cermet tools for steel machining have greatly improved the productivity and efficiency of the metal removal process. The performance of a number of cermet materials, which principally are based on refractory metal carbides or nitrides bonded with cobalt, nickel, molybdenum, or alloy binders, inherently is limited by the chemical interaction between the hard phase and steel workpiece materials. This becomes particularly evident as increased cutting speeds generate more heat, increasing the chemical reactivity of both the tool material and the workpiece. Such chemical reactions between the cutting tool and steel workpiece accelerate wear and reduce crater resistance of the tool.
Attempts have been made to utilize alumina ceramics and alumina-based composites such as alumina-titanium carbide composites for use as cutting tools for steel machining. The broader use of this class of materials, however, has been restricted by their inherent brittleness.
Of particular concern has been the need for cutting tools suitable for machining of high nickel superalloys. The high temperature nickel based superalloys, for example Inconel.RTM. alloys (available from Huntington Alloys, Inc., Huntington, W. Va.), present the advantages of deformation resistance and retention of high strength over a broad range of temperatures. Because of their high strength at elevated temperatures, however, these alloys are much more difficult to machine than steels.
Ceramic-metal (cermet) tools, for the most part, have shown only limited effectiveness in machining of nickel based alloys. These cermet materials are based principally on refractory metal carbides or nitrides bonded with cobalt, nickel, molybdenum, or alloy binders. Commercially available cutting tools, for example cobalt cemented tungsten carbide, can be utilized for such machining only at relatively low cutting speeds and hence provide low productivity.
Attempts have been made to utilize alumina ceramics and alumina-based composites such as alumina-titanium carbide composites for use as cutting tools for high temperature nickel based superalloy machining. The use of this class of materials, however, has been restricted by their inherently low fracture toughness, limiting the usable feed rate and depth of cut. Alumina-silicon carbide whisker composites have provided some increase in fracture toughness, but the whisker component, due to its fibrous nature, requires extremely careful handling to assure safety.
Accordingly, it would be of great value to find a cutting tool suitable for machining difficult-to-work metals such as high temperature nickel based superalloys using a cutting tool body which exhibits improved chemical wear resistance and performance when compared to conventional ceramic metal-cutting tool materials, improved fracture toughness compared to known alumina-titanium carbide composites, and improved ease of fabrication compared to known alumina-silicon carbide whisker composite materials. The body described herein is directed to achieving such a cutting tool.